Circuit breaker



March 1l, 1952 H. D. DORFMAN x-:r A1.

CIRCUIT BREAKER Filed D80.

Insulation Il |04 I5 INVENTORS Hiller D.Dorfmonond WITNESSES1.

William D.Po1on. G B N LVZ ATTORNE Patented Mar. 11, 952

CIRCUIT BREAKER Hiller D..Dorfman and'William D. Patton, Beaver,

Pa., assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., afcorporation of Pennsylvania Application Decemberv 10, 1949,'Serial No. 132,342

(Cl. 20G-8.8)

6 Claims.

Thisinvention relates to circuit breakers, and more particularly to circuit breakers for con.- trolling lighting and moderate power. circuits.

An object of the invention is to provide a circuit breaker embodying an improved thermally and magnetically responsive trip device having the magnetically responsive means supported partially on the thermally responsivemeans.

Another object of the invention is to provide an improved thermally-and magnetically responsive trip device wherein operation kof the magnetic element does not require bending of the thermal element and avoids the possibility of the thermal element taking a permanent set due to its being bent when in a heated condition.

Another object of the invention is to provide a trip device having an armature movable against the bias of a spring other than the thermal element to permit the use of a stiffer thermal element without requiring a large magnetic force for magnetic tripping.

Another object of the invention is to provide a circuit breaker which is simple, safe and reliable in operation, and which is inexpensive to manufacture.

The novel features that are considered characteristic of the invention are set forth in particular in the appended claims. The invention -itself, however, both as to structure and operation, togetherwith additional objects and advantages thereof, will be best understood vfrom the following detailed description thereof when read kin conjunction with the accompanying drawing.

In said drawing the figure isa side elevational view, partly insection, of a circuit breakerembodying the principles of the invention,

Referring to the drawing, the three-pole vcircuit breaker illustrated is mounted in an insulating housingk comprising a base v|I anda removable cover |3 both of molded insulatingmaterial. The base and cover are provided with aligned barriers I5 and I1 which serve to divide the housing into three compartments, one for each pole of `the breaker.

Each pole of the breaker (only one being shown) includes astationary contact I9, an arc extinguisher 2| and a movable contact 23. The stationary contact is mounted on the inner end of a conducting strip 25, the other end of `which is secured to a terminal 21. The arc drawn by the movable contact is deionized andV extinguished in. a .well-known manner.

The movable contact 23 isfcarried on the free endy of` a vresilient contact arm 29 which .is secured to a U-shaped-switch member 3|. The

movable contact is electrically. connected by a flexible conductor 33 to the current-responsive trip device for the associated pole which will be hereinafter described.

The other terminal of the trip device is electrically connected to a conducting strip 35 which is connected to a terminal 31. The switch arms for the three poles of the breaker are of substantially identical construction, hence, only one pole has been illustrated and described.

The three movable switch members 3| are mounted for unitary rotationabout a common axis by means of a sectional pivot shaft 39, the center section of which is supported in the. side elements of aYU-shaped-main-frameM secured to the base in the center compartment. The switch members for the outer poles of the breaker are not shown but are secured to the outer sections of the pivot shaft 39, and are mechanically connected to the center pole switch member but insulated therefrom by insulating connecting hubs 43. A stop-pin 45 extending through the frame 4-| cooperates with projections formed on the center pole switch member 3| to limit opening movement of the switch members.

The single operating mechanism-for all three poles is mounted on the U-shaped main frame 4| and comprises a U-shaped operating member 41, the two legs of which are pivoted on the sides of themain frame by pivot members 49, a releasable carrier 5| pivoted on the main frame by means of a pivot shaft 53 andnormally releasably restrained by a U-shaped latch 13, a pair of toggle links 55 and 51, and a pair of overcenter springs 59 (onlyone being shown). The toggle links 55-51 are pivotally connected to'- gether by a knee pivot pin 6|. The innertoggle 55 is pivotally connected by a pivot pin 63 to the center pole switch member '3|. The toggle link 51 is pivotally connected at its outer end by a pivot pin to the releasable carrier 5|. The overcenter springs 59 have their outer ends connected to the bight portion of the U-shaped op'- erating member, and their inner ends are connected to the knee pivot pinV 6| of the toggle 555-51. An operating handle 61 of molded insulating material is secured to the outer end of the operating member 41. The operating handle 61 is provided with a handle portion which extends through an opening 69 in the cover |3. The operating handle 61 is also provided with an arcuate portion 1| which serves to substantially close the opening 59 in all positions of the handle. Lugs 12 are struck out from the sides of the main frame 4| to limit the opening and closing movement of the operating-member 41.

The breaker contacts are manually opened by clockwise movement of the operating handle from the position in which it is shown in Figure 1. This movement carries the line of action of the overcenter springs 59 across to the right of the pivot pin 65 whereupon the force of the springs causes collapse of the toggle 55-51 thereby moving the movable contacts to the open position With a snap action. The contacts are closed by counter-clockwise movement of the handle 61 to the Figure l position. This moves the line of action of the springs 59 across to the left of the pivot 85; consequently, the springs actuate the toggle 55-51 to its extended overset position shown, thereby moving the movable contacts to the closed position with a snap action.

The latch means of the circuit breaker includes the latch 13 pivotally mounted on a pivot pin 15 supported in the main frame ll. An extension 19 of the latch is provided with an opening 8|, one edge of which engages the free end of the carrier 5| and restrains the carrier in normal position. The latch 13 is also provided with an extension 83 having an opening 85 therein. lA trip bar 81 of molded insulating material and common to all of the poles of the breaker is mounted for rotation by means of a shaft 89 molded therein, the ends of which are mounted in brackets 9| (only one being shown) secured to the base II of the housing. An arcuate latch member 93 is molded into the trip bar in alignment with the opening 85 in the main latch 13. In the latching position of the parts (Fig. 1), the carrier 5| is latched by the main latch 13 Which, in turn, is held in latching position by the latch member 93. A spring 95 coiled about the pivot pin 15 biases the main latch 13 in unlatching direction and also biases the trip bar to latching position. The trip bar 81 is provided with a plurality of projections 91, one for each pole of the breaker, molded integral therewith.

Each pole of the breaker is provided with an individual trip device including a, current-responsive bimetal element |I having a mounting foot formed thereon secured to the base by means of a scr-ew |02 engaging a threaded insert |04 molded in the base I I. The bimetal element |0| is electrically connected in the circuit of the breaker in series relation with the breaker contacts. The free end of the bimetal is connected by means of a flexible conductor |03 to the conducting strip 35, and the mounting foot of the bimetal element is connected by the iiexible conductor 33 to the movable contact 23. An adjusting screw |05 is threadedly mounted in the free end of the bimetal element I0 I.

. Extending substantially parallel to, but spaced from, the high expansion side of the bimetal element |0| is a spring member |01 which also has a mounting `foot formed thereon and secured to the base II by means of the same screw |02 which mounts the bimetal element on the base. The free end of the spring |01 is formed into a loop as at |09 so that the end of the spring extends downwardly between the rounded end oi the adjusting screw |05 and the projection 91 on the trip bar 81. The spring |01 has a clearance opening |08 therein forY the adjusting screw to permit movement of the spring relative to the bimetal element. Insulating buttons are mounted on the spring |01 between the screw |05 and the projection 91 to insulate the spring |01 from the bimetal element.

`Electromagnetic means is also provided to instantaneously trip the breaker. VThe electromagnetic trip means comprises a U-shaped mag'- net yoke ||3 rigidly mounted on and partially surrounding the bimetal element I0 I, and an armature ||5 mounted on the spring |01 adjacent the magnet yoke I I3.

Upon the occurrence of an overload current below a predetermined value of, for example, 1000% of normal rated current, the bimetal element is heated and when heated a predetermined amount deflects toward the left. As the bimetal element deects, the rounded end of the adjusting screw |05 engages the adjacent insulating button and eXes the spring |01 until the button engages the projection 91 and rotates the trip bar 81 counter-clockwise to tripping position. When the trip bar 81 moves to unlatching position, the latch member 93 moves from under the righthand end of the latch extension 83, thereby permitting the main latch 13 to release the carrier 5I. The carrier 5I is rotated in a counter-clock- Wise direction about its pivot 53 during which movement the pivot 65 is moved to the left of the line of action of the springs 59 whereupon the toggle 55-51 collapses and eiects opening of the breaker contacts. Y

The trip bar 81 is actuated by the electromagnetic means I I3-I I5 to instantaneously trip the breaker in response to overload currents of, for instance, 1000% or more of normal rated current. Upon the occurrence of such an overload current, the electromagnetic means is energized by the current flow through the bimetal element IOI and the armature II5 is instantly attracted to the magnet yoke II3. This action bends the spring |01 and causes the free end thereof to engage and instantaneously actuate the trip bar 81 to trip the breaker. It is noted that the spring |01 is flexed by the electromagnetic means to trip the breaker without requiring bending or placing any undue stress on the bimetal element.

The carrier lever 5I must be reset to latched-up position before the breaker can be closed. This is effected by movement of the handle in a clockwise direction beyond the 01T position. During this movement, a projection 99 on the operating member 41 engages and moves the carrier 5I back to the latching position.

During the latter part of the resetting movement, the free end of the carrier 5| moves into and engages the lower edge of the opening 8| in the main latch 'i3 and restores the main latch to latching position, and the spring then returns the trip bar 81 to its latching position shown. The circuit breaker may then be closed by movement of the handle to the on position in the previously described manner.

The resilient member is exed by the magnetic means to trip the breaker without requiring bending or placing any undue stress on the bimetal element. The use of the biased or resilient member, which moves magnetically independently of the relative stiff bimetal element, makes it possible to obtain sensitive magnetic tripping. This gives 10W cost by making possible the use ofthe bimetal element as a single turn energizingcoil for the tripping magnet in place of the multi-turn coil that would be required to give the necessary ampere turns if the relatively stiff bimetal had to be bent.

The tripping point of the bimetal element of each modification may be independently varied by means of the adjusting screws without alter.

ing the instantaneous magnetic tripping point,

' that is, without changing the magnetic air gapof the electromagnetic means.

caesaer:

`From the foregoing itfwill be seen that there'is provided-'an improved circuit breaker of sim-ple and inexpensive construction wherein operation of the electromagnetic trip means applies no bending stress to .the thermal element and avoids the possibility of the thermal element taking a permanent set due to its being stressed when in a heated condition. Also the tripping magnetic means is movable-against the bias of a biased member other than the thermal element, so that a stiffer thermal element may be used Without requiring a greater magnetic force for magnetic tripping.

While the invention has been disclosed in accordance With the provisions of the patent statutes, it is to be understood that various changes in the structural details vand arrangement of parts-thereof may be made without departing from some of the essential Afeatures of the invention.

We claim as our invention:

1. A circuit breaker having relatively movable contacts and means releasable to effect opening of said contacts, trip means including a trip bar normally releasably restraining said releasable means and movable to cause release of said releasable means, a trip device comprising a bimetal element having one end supported, adjusting means on the free end of said bimetal element disposed adjacent said trip bar, a resilient member having an end supported adjacent the supported end of said bimetal element and extending along but spaced from said bimetal element on the side opposite said trip bar, the free end of said resilient member being looped around the free end of said bimetal element and disposed between said adjusting means and said trip bar,` said resilient member having an opening therein through which said adjusting ymeans projects to permit relative movement ofsaid bimetal element and said resilient member, said bimetal deiiecting when heated a predetermined amount in response to overload currents below a predetermined value to cause said adjusting means to engage the free end of sai-d resilient member `and bend said resilient member to move said-trip bar, a f rst magnetic member mounted on said bimetal element, a second magnetic member mounted on said resilient member, said magnetic members being operable in response to overload currents above said predetermined value to instantaneously bend said resilient lmember and move said trip bar, and said adjusting means being adjustable without moving said bimetal element or said resilient member to vary the amount of deection of said bimetal element required to move said trip bar.

2. A circuit breaker having relatively movable contact means and means releasable to effect opening of said contact means, a trip member having a latch element thereon normally restraining said releasable means and operable to effect release of said releasable means, a trip device for operating said trip member comprising a bimetal element supported at one end, adjusting means on the free end of said bimetal element, a resilient strip having one end supported adjacent the supported end of said bimetal element, a main portion of said resilient strip extending along the high expansion side of said bimetal element but spaced therefrom and said resilient strip having an abutment disposed between said adjusting means and said trip member, said bimetal element deecting when heated a predetermined amount in response to overload currentsbelow a predetermined value to causezsai'c adjusting means to engage said abutment-and move said resilient strip to thereby cause said abutment to engage` and actuate said tripmember, electroresponsive means comprising a pair of magnetic members one mounted on said bimetal element and the other mounted on said resilient strip, said electroresponsive means being energized in'response to overload currents above said predtermined value iiowing through said bimetal element and operable when energized to cause said abutment to engage and instantaneously actuate said trip member, said adjusting means being adjustable to vary the thermal tripping point without changing the position of said bimetal element or said resilient strip.

3. A circuit breaker including relatively movable contacts, a releasable member operable when released to effect opening of said contacts, a trip bar normally restraining said releasable member and operable to eiect release of said releasable member, a trip device including a bimetal elementhaving one end supported and electrically connected to be traversed by the current of the circuit, an adjusting screw on said bimetal element adjacent the free end thereof, electroresponsive means comprising a pair of magnetic members on opposite sides of said bimetal element and energized by the current ow therethrough, both of said magnetic members being movable, a strip oi spring material extending along the high expansion side of said bimetal element, said strip having a portion disposed between the end of said adjusting screw and said trip bar, said spring having an opening therein through which said adjustingV screw extends to permit relative movement of said bime-tal element and said spring, one of said magnetic members being mounted on said spring strip and movable toward the other magnetic member to cause bending of said spring strip against its normal bias to the point where said portion engages and actuates said trip bar,.thermal bending of said bimetal element causing said adjusting screw to engage said portion of said spring and actuate said trip bar, said adjusting screw being adjustable to vary the thermal tripping point without disturbing the position of said bimetal element and said spring and without-disturbing the magnetic airgap of said magnetic members.

4. A circuit breaker comprising separable contactmeans and means releasable to effect automatic opening of said contact means, a trip member releasably restraining said releasable means, current responsive means for actuating said trip member to release said releasable means in response to overload currents below a predetermined value comprising a thermally responsive element having one end supported, adjusting means mounted on said thermally responsive element near its free end, a spring member having one end supported adjacent the supported end of said thermally responsive element and having an opening therein surrounding said adjusting means to permit relative movement of said thermally responsive element and said spring member, a main portion of said spring member being disposed along the high expansion side of said thermally responsive element and having an abutment disposed on the low expansion side of said thermally responsive element between said adjusting means and said trip member, said thermally responsive element flexing when heated a predetermined amount to cause said 7 adjusting means to engage said abutment and move said spring member to actuate said trip member and eiect release of said releasable means, cooperating magnetic members mounted on said thermally responsive element and on said spring member, said magnetic members being operable in response to overload currentsv above said predetermined value to instantaneously move said spring member independently of said adjusting means and release said releasable means, and said adjusting means being adjustable to vary the thermal tripping point of said breaker without changing the positions of said thermally responsive element and said spring member and while the magnetic tripping point remains constant.

5. A circuit breaker comprising separable contact means and means releasable to eiect opening of said contact means, current-responsive means for effecting release of said releasable means in response to Voverload currents below a predetermined value comprising a thermally responsive member having one end supported and a resilient member having one end supported adjacent the supported end of said thermally responsive member, adjusting means mounted cn said thermally responsive member and being engageable with the other of said members, said other member being provided with an opening surrounding said adjusting means to permit relative movement of said members, a main portion of said resilient member being disposed on one side of said thermally responsive member and having an` abutment disposed on the opposite side of said thermally responsive member, said thermally responsive member ilexing when heated to cause said adjusting means to engage said abutment and bend said resilient member to eiect release of said releasable means, a pair of magnetic members, one of said magnetic members being mounted on said thermally responsive member and the other of said magnetic members being mounted on said resilient member, said magnetic members being operable in response to overload currents above said predetermined value to instantaneously bend said resilient member and release said releasable means, and said adjusting means being adjustable to adjust the tripping point of said thermally responsive member without disturbing the initial position of either of said members and while the magnetic tripping point remains constant.

, 6. A circuit breaker comprising relatively movable contact means and means releasable to effect opening of said contact means, a trip bar having latch means thereon normally restraining said releasable means, said trip bar being movable to release said releasable means, a trip device for moving said trip bar comprising a bimetal element supported at one end and electrically connected to be traversed by current, electroresponsive means comprising a pair of magnetic members on opposite sides of said bimetal element and energized by current flow therethrough, one of said magnetic members being mounted on said bimetal element, both of said magnetic members being movable, a strip of spring material having a main portion disposed along the side of said bimetal element away from said trip bar and having an abutment disposed between said bimetal element and said trip bar, the other of said magnetic members being mounted on said spring strip to provide an air gap between said magnetic members, one of said magnetic members being movable toward the other magnetic member causing bending of said spring strip against its normal bias and causing said abutment to engage and move said trip bar, thermal bending of said.

bimetal element causing said bimetal element to engage said abutment and cause said abutment to engage and move said trip bar, and adjusting means mounted on said bimetal element adjustable to vary the tripping point of said bimetal element without changing the positions of the bimetal element and the spring strip and while the magnetic air gap remains constant.

HILLER D. DORFMAN. WILLIAM D. PATTON.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,027,238 Lindstrom Jan. 7, 1936 2,035,743 Frank Mar. 31, 1936 2,184,372 Von Hoorn Dec. 26, 1939 2,328,458 Jackson et a1 Aug. 31, 1943 2,360,684 Jennings Oct. 17, 1944 2,416,163 Dyer et al Feb. 18, 1947 2,439,511 Green Apr. 13, 1948 FOREIGN PATENTS Number Country Date 616,133 Germany July 20, 1935 

